A heat exchange and pressure relief device therefor



United States Patent Inventor: Robert S. Wentworth, Jr.

' Wilmington, California Application No.: 781,153 Filed: Dec. 4, 1968 Patented: Aug. 4, 1970 Assignee: Borg-Warner Corporation Chicago, Illinois a Corp. of Delaware A HEAT EXCHANGE AND PRESSURE RELIEF [56] References Cited UNITED STATES PATENTS 2,888,251 5/1959 Dagin 165/74 Primary Examiner- Robert A. O'Leary Assistant Examiner- Charles Sukalo AttorneyDonald W. Banner, Lyle S. Motley, C. G. Stallings and William S. Mc Curry ABSTRACT: A pressure relief device for a heat exchanger wherein the housing consists of a cover, and a case adapted to seat against the cover; coils for conducting hot fluid through the housing for cooling the fluid; a cooling fluid in said housing surrounding the coils; and attaching means including shear DEVICE E R means operable to shear upon occurrence of excessive pres- 7Claims6Drawmg sure in said housing, allowing the case to separate from the US. Cl. 165/74, Cover to release the pressure in said housing; stop means limit- 165/163 ing the travel of said case under influence of said pressure, and Int.Cl. F28d1/06 decelerating means decelerating the movement of the case Field ofSearch 165/11,?6, prior to its reaching the travel limit permitted by the stop 74,134, 163,175,160 means.

57 so 55) i Patented Aug. 4, 1970 Sheet I INVENTOR, I 205587 5. mam/0 22% we.

BY L 1m US PATENT 3,522,840

A HEAT EXCHANGE AND PRESSURE RELIEF DEVICE THEREFOR CROSS-REFERENCE TO RELATED APPLICATION The invention is an improvement in a heat exchanger and is illustrated as an improvement of the subject matter of United States Patent Application Serial No. 749,120, filed July 31, 1968, by Robert S. Wentworth, Jr. and entitled Heat Exchanger.

BACKGROUND OF THE INVENTION This invention has to do with releasing excessive pressure in the housing of a heat exchanger, and controlling the movement of the parts thereof to prevent them becoming projectiles endangering persons and objects in the line of travel.

ln heat exchangers of this type wherein fluid under pressure and high heat is conducted through the heat exchanger in a coil which is surrounded by cooling fluid, a rupture of the coil may result in a sudden increase'of pressure in the housing, possibly the sudden creation of superheated steam. In such event something has to give, and usually the case will be fragmented or the means attaching the case to the cover will be destroyed and the case and attaching means or other parts will be propelled outwardly at tremendous speeds. Anyone in the line-of-flight could be severely injured or killed, and adjacent equipment damaged or destroyed, unless means are provided to release the pressure instantly and control the travel or movement of the case and other parts to prevent them becoming projectiles.

SUMMARY It is an object of the present invention to provide an arrangement, operable by an excessive pressure occurring in the housing, to cause the case to separate from the cover and allow the pressure to escape, thus preventing fragmentation of the case and to provide means limiting the travel of the case to prevent it from becoming a projectile.

It is an object to provide an attaching means attaching the case to the cover wherein under normal operation the interior of the housing is maintained at proper pressures and securely sealed, but which attaching means has a shearing element which will shear and release the case, and will allow the case to separate from the cover upon the contingency of buildup in pressure past an acceptable maximum.

It is a further object in connection with the attaching means to provide a stop means which limits the travel of the case under shear conditions, but will permit the pressures therein to escape safely.

It is a further object of the invention to provide a damping or decelerating means which becomes effective before the case reaches the limit of travel permitted by the stop means, and will effectively slow down the speed and stop the travel of the case before it reaches the limit permissible, thus preventing the case from destroying the limit or stop means and becoming a projectile.

It is an object in. this connection to provide a housing comprising a case and cover wherein the case is attached to the cover by an elongated bolt having a head spaced outwardly from the case and cover which acts as a stop means for the outer limit of travel of the case, and wherein shear means holds the case in position, but which shear means will release under excessive pressure, and further having a decelerating means to slow down or decelerate the travel ofthe case.

It is an object of the invention to provide an arrangement wherein the housing contains coils with liquid under high pressure and high temperatures, and the coils are overlapped with a spacer sheet between each layer, and wherein the housing is provided with a blind bore having a bolt therethrough attaching the case to the cover, with the bolt having a head serving as a limit stop in the event the case is propelled outwardly, and also having a ring thereon with a shear pin through the bolt and resting against the ring to form a holding means holding the case to the cover, and further providing for a sleeve of distortable material forming a decelerating means located between the bolt head and the ring and adapted to slow down and stop the case in the event the pressures cause the shear pin to shear and the case to be propelled outwardly.

It is an object of the invention to accomplish the above purposes with a relatively simple arrangement which is easy to use and comparatively inexpensive, and which is fully effective for the purposes intended.

Other objects and advantages of the invention will be hereinafter described or will become apparent to those skilled in the art and the novel features of the invention will be defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view illustrating the present invention the view being taken on the line l-1 of FIG. 2 looking in the direction of the arrows, the view also having a mounting bracket shown in broken lines;

FIG. 2 is an end elevational view illustrating the cover or base of the heat exchanger shown in FIG. 1 as incorporating the present invention;

FIG. 3 is a fragmentary sectional view taken on the line 3--3 of FIG. 2, looking in the direction of the arrows;

FIG. 4 is a fragmentary rear end view, partly in cross-section and showing the arrangement of the shear means, the view being taken on the line 4--4 of FIG. 1 looking in the direction ofthe arrows;

FIG. 5 is a fragmentary sectional view taken on the line 5-5 of FIG. l looking in the direction ofthc arrows; and

FIG. 6 is a longitudinal sectional view showing the device of FIG. l in its condition subsequent to the operation shearing the shear means and travel of the case to its outer limit to relieve excessive pressure within the housing.

DESCRIPTION OF THE PREFERRED EMBODlMENTS Referring next to the detailed construction shown in the various drawings and referring first primarily to FIG. l, there is here disclosed a housing 21 which comprises a case 22 and a cover 23. The case, in the arrangement shown, has an annulus 24 formed by an outer cylindrical wall 25 and a radially inwardly spaced inner cylindrical wall 26 concentric with the wall 25. There is an end wall 27 extending between the outer wall 25 and the inner wall 2a which. for the purposes of this application, will be described as being on the rear or outer end of the case 22.

The bore formed by the inner cylindrical wall 26 is joined at its other end; that is, its inner end, with a closure wall or web usually herein referred to as the web 28, and forming with the inner cylindrical wall 26 a blind bore or recess 29 open at its outer end,

The web ZR-preferably is drilled or otherwise provided with a hole or opening 31 to accommodate a bolt or other fastening means, herein shown as an elongated bolt 32, whereby the case 22 may be attached to the cover 23.

The cover 23 is also provided with an opening or hole 33 which, when the case is seated on the cover, is in alignment with the hole 3i in the web 28. The bolt 32 is-threaded on the end which extends through the cover 23, and the bolt 32 as above mentioned is preferably elongated as shown in the drawings, and provided with a nut 34 on its threaded end and a head 35 on its outer end, The head 35 serves as a stop limit to limit the outward travel of the case 22, as hereinafter described. It will be noted that the bolt extends outwardly a preselected distance from the web, preferably having the head 35 located at or near the outer end of the case. The reasons for this will be apparent from further description.

A grooved ring 36 is carried by the bolt 32 and is adapted to seat against the web 29 as shown in FIGS. l and 3.

As will be apparent from FIGS. 1, 3, and 4, the bolt 32 is drilled to receive a shear pin 37, which shear pin seats within the groove, here numbered groove 38 (see FIG. 6).

The groove 38 is preferably of approximately the same diameter as the shear pin 37 so that the groove will support the shear pin over one half of its circumference. This allows the use of a smaller size shear pin than would be necessary in the event the groove were not provided, and correspondingly the hole through the bolt 32 may be smaller, thus not unduly weakening the bolt. I

Also carried on the bolt 32 is a tube 39 of deformable material, preferably copper or other suitable metal, which is provided with indentations 41 which serve both the purpose of retaining the tube, 39 by friction or pressure on the bolt adjacent the head 35, and also conditions the tube 39 for the proper crushing or deforming action when the case and ring travel up the bolt and strike the end of the tube 39. This arranger'nent of the tube will be clear from FIGS. and 6 and will be described more in detail later herein.

Referring next to FIGS. l, 2 and 3 in particular, and especially to FIGS. 1 and 2, there is provided a coil' of tubing 42 which, in the arrangement shown, enters the housing 21 through a hole 43 in the cover 23, extends outwardly in a spiral winding and inwardly on a reverse spiral diametrically inward of the outer spiral, and leaves the housing 21 through the hole 44 in the cover 23. In usual practice, liquid to be cooled is carried by the coil. This liquid may be under several hundred degrees of temperature; for example, 400F., and under high pressure, possibly 2500 or 3000 p.s.i.g. b

As is clear from FIGS. 2 and 3, a coolant liquid enters the housing through the port 45, flows around the coils 42 and exhausts through the outlet port 46. This coolant, which is frequently water, may be under pressure such as exists inthe water mains servicing the area where the device is used possiblyunder pressure of up to 150 p.s.i.g., against which the shear means must hold without shearing. The ports 45 and 46 are tapped, and (while not shown) port 45 is adapted to be connected to a source of coolant, and port 46 to a drain or other means for disposing of such coolant.

In thearrangement shown, the coils 42 are separated by a spacer sleeve 47 which, when the housing is assembled, seats against the cover 23 at its innner end and is partly cut away at its outer end to allow the coils 42 to pass around the outer end and further to allow the cooling fluid to flow from the area surrounding the inner portion of the coils to the area surrounding the outer portion of the coils.

The cover 23 is usually provided with a mounting bra'cket 48 on-the cover 23, which mounting bracket 48 is shown in FIG. I in dotted lines, by means of which the housing assembly may be attached to a suitable support.

It will also be noted that the case 22 is provided with O-rings 49 and 5| which are adapted to seat against the cover 23 and form liquid-tight seals circumferentially outwardly and inwardly respectively of the annulus 24, thusassuring thelretention of the liquid in the annulus. Y

The case 22 as shown here, has a vent hole 52 in which is inlayer of coils, and the coils connected to a source of fluid to be cooled. The case 22 is then inserted over the coils, with the web 28 and seals 49 and 51 against the outer face of the cover The bolt 32 with the decelerating means here shown as tube 39, mounted thereon adjacent .the head 35 and with the shear pin 37 extending through the bolt and resting in the groove 38 of the ring 36, is then inserted in the blind bore with the threaded end of the bolt extending through the cover 23 and with the ring 36 resting against the outer face of the web 28. The nut 34, is then tightened to draw the case 22 firmly against the-cover 23, but not sufficiently to shear the shear pin 37.

The coolant connections (not shown) are then completed and the device is ready for operation. It is noted that the shear pin sure fluid from the coils into the cooling liquid in the annulus.

Such rupture of the coil may result in the instant formation of superheated steam which, if adequate relief means were not available, would either fragment the case 22'or shear the head of the retaining bolt (in the previous forms wherein no shearmeans, or inadequate shear means, is provided) causing the case to be propelled at tremendous speed outwardly. In the arrangement here provided, a sudden increase in pressure would shear the shear pin 37, allowing the case 22 and ring 36 to be propelled lengthwise of the bolt. This would instantly release v the pressure in the annulus. However, in the absence'of a decelerating means, the force of propulsion of the case would I tend to shear the head 35 from the bolt, and the stop ring, bolt head, and case could become a very dangerous projectile. Thus a decelerating means is necessary or at least desirable to slow down the case 22 and ring 36 and prevent them fromslamming into the head 35 of the bolt 32 with excessive force. Such a means has been provided in the tube 39 .of copper or other similar material which will collapse and distort and serve as a decelerating means slowing down and generally stopping the ring and the case before they reach the limit means; that is, the head 35 of the bolt. I

While copper is a suitable and preferable substance for the sleeve 39, other deformable materials; usually 'metal, may be made toserve the same purpose.

It is noted that while it is a less desirable arrangement, the bolt 3.2 and its ring 36, decelerating means (tube 39) and shear pin 37, could be reversed so that the head 35 is on the other side of the cover 23. In such an arrangement, of course, the entire pin would be drawn against a lefthand surface (in the illustration shown) of the cover 23. However, the bolt 32 would not be protected and out of the way as it is in the bore of the present arrangement, and-it would be more difficult to assemble.

It is further noted that the ring 36 could possibly be dispensed with, but since the groove 38 is desirable, provision would have to be made therefor in the face of the web 28, and the arrangement would not be as easy to assemble or as satisfactory. Further, the ring 36 does tend to distribute thepressure around the entire face of the web beneath the ring, whereas elimination ofthe ring would tend to place the forces on only a very small part of the web.

lncidentally, while the principles of the invention may be adaptable toother forms of heat exchangers,they are particularly valuable in the form of heat exchanger shown here primarily for the reason that the coils and spacer sleeve tend to block or otherwise interfere with the escape of any steam or pressure'to a greater degree than would normally be present in .other arrangements. This'makes the invention particularly valuable for the arrangement shown.

. lclaim:

1. In a heat exchanger or the like having a housing comprising a cover and a case adapted to seat on said cover, means comprising coils for conducting hot fluid to be cooled through said housing, a cooling fluid in said housing surrounding said coils, and means attaching provements wherein:

a) said attaching means includes a shear means operable to shear upon the occurrence of pressure exceeding a predetermined maximum in said housing, to release said case allowing it to separate from said cover; b) stop means limiting the travel of said case upon its separating from said cover; and c) a decelerating means decelerating the speed of move ment of said case after it separates from said cover and before it reaches the travel limit imposed by said stop means.

said case to said cover, those im- 2. In a heat exchanger or the like as claimed in Claim 1, wherein said shear means comprises a ring on said attaching means and a shear pin carried by said attaching means and resting against said ring.

3. In a heatexchanger or the like as as claimed in Claim 1, wherein said decelerating means comprises a tube on said attaching means located between said stop means and said shear means, and constructed of deformable material adapted to deform under the force created by movement of said case after it separates from said cover.

4. In a heat exchanger or the like as claimed in Claim 2, wherein said decelerating means comprises a tube on said attaching means located between said stop means and said shear means, and constructed of deformable material adapted to deform under the force created by movement of said case after it separates from said cover.

5. In a heat exchanger or the like as claimed in Claim 4, wherein the stop means limiting the travel of said case upon separation from said cover comprises the head of a bolt forming a part of said attaching means, spaced longitudinally of said attaching means from said case whereby said case moves longitudinally of the bolt after it separates from said cover and before it reaches said stop means.

6. in a heat exchanger or the like as claimed in Claim 5, wherein the decelerating means comprises a tube of deformable material having means frictionally engaging said bolt and holding said deformable'tube positioned thereon adjacent said bolt head.

7. In a heat exchanger or the like as claimed in Claim 2, wherein said ring contains a groove adapted to receive such shear pins 

